1. Field Of The Invention
The invention relates to seat cushions. More particularly, it relates to multi-piece cushion elements that are constructed of polyurethane or other plastic foams.
2. Description Of The Art
The use of resilient polyurethane foam for seat cushion interiors is well known. However, a number of difficulties have been encountered in using such foams, chief among these being irregular I.L.D compression of available molded foam, unacceptably short wear life of the cushion, and the unacceptable feel which such cushions give (e.g. due to skinning on molded foam and/or compression factors).
Some problems associated with using foam cushions have been overcome by cutting the cushion interior elements out of larger commercial size "buns". These buns are produced by allowing the polyurethane foam to freely expand to produce a lower I.L.D. compression foam near the upper part of the bun. After the outer most skin is trimmed off, the upper most portion of the bun is cut away and used for the cushion. This softer, skinless foam is much better for use as cushion material. However, it commands a premium price. Also, as its thickness increases, it begins to give the user more and more of the feel of sitting on an inflated basketball.
In recent years there has been a movement towards styling requiring extremely thick cushions that are highly "crowned". Aside from the problems discussed above with respect to feel and price, this causes a tendency for the cushion to wear less well under repeated compression (apparently due to the rubbing of the material against itself). Another problem is that cutting large foam blocks into thick crowned surfaces requires specially designed machines, and generates considerable waste materials.
Some time ago there were attempts to produce foam cushion elements that had spaced internal foam components (see U.S. Pat. Nos. 2,835,313 and 2,858,881). However, these prior art systems were not widely adopted, apparently due to the costs involved in providing the complex shapes or installing the components, the deficiencies in the available foam, the deficiencies in providing a suitable feel to the user, and other reasons. Thus, it can be seen that a need exists for a plastic foam cushion element that uses less foam than a solid block cushion element, is resistant to wear, has a high crown, feels to a user like a high quality cushion, and is inexpensive to produce.